Before stepping into that mess. Check with the OHP and find out what type of problems you will get into on title. The 2nd gen frame would have different VIN from the cab. Most states have laws covering that problem. Cab VIN and frame VIN's must match. Find out if OK has a assembled motor vehicle provision in the laws.
I went threw this a while back when I changed my cab.
The short answer is yes. Its called a change of body